Indian Journal of History of Science, 51.3 (2016) 431-442 DOI: 10.16943/ijhs/2016/v51i3/48846

Mud Paintings of Bhaja Caves: Composition and Performance Characteristics

M Singh*, S Vinodh Kumar**and Sujata Waghmare***

(Received 30 May 2016; revised 05 August 2016)

Abstract The historic plaster of Bhaja caves dated back to 1st century BC to 3rd century AD were investigated for their mineralogical, micro – structural and chemical characterisation. The analytical studies were performed using petrological microscope, thin section analysis, XRF, Laser particle size analyser, FTIR, XRD and scanning electron microscope. The traditional mud plaster is applied in two layers and thickness of inner layer depends on the topography of the basaltic stone surfaces. From the analytical examinations, it appears that in high rain fed regions of ’s Western Deccan, fine clayey (>65%, 20-28% and silt 7-15%) has been sourced for the preparation of earliest mud plaster of Bhaja caves and its properties modified by deliberate mixing of slaked , sand and proteinaceous adhesive to enhance cementing properties. SEM photomicrographs reveal presence of elongated kaolinitic ‘verm’ and inter wired filamentous clay ribbons of illite- sepiolite in the plaster. The shrinkage property of the plaster has also been modified by addition of rice husk as vegetal additives. The present study favours methodological approach for preparing compatible mud plaster needed for the restoration of Bhaja caves. Key words: Calcite, Clay soil, Illite-sepiolite, Kaolinite, Mud plaster

1. In t r o d u c t i o n lying out and cutting the caves and not fully aware Bhaja represents the earliest cave about the problems presented by flawed basaltic architecture in Western Deccan after a century of scrap (Sundarajan, 1957-59). As technicians abandonment and decline of this artistic form. The have to struggle in the beginning during their site benefited from its position on an important first major excavation at Bhaja, the caves appear maritime trading point connecting the parts of to have a rather irregular structure as a result of western India with the cities in the interiors and poor planning and numerous after-thoughts with became a stopping place for itinerant pilgrims, very simple architectural elements. However, monks and merchants. Beside a Brahmanical caves year by year after gaining initial experiences the at Udayagiri near Vidisha in neighbouring Madhya excavators incorporated more complex and up Pradesh, cut a little over fifty years earlier, no other to date forms. They introduced now peristyles to  sites were excavated in whole of western Deccan Vih ra, introduced beautiful ornamental pillars for about three hundred years. Architects and and sculptures were lavishly decorated. worksmen employed at Bhaja had to re-discover The caves of Bhaja also represent the the technique of rock cutting that has been partly very first example in Western India where earthen lost to living memory. plaster technology was practiced for decorative As a consequence, the artists were totally purposes. The techniques and composition of the unfamiliar with the procedures needed to both earthen plaster were subsequently improved in the

*Researcher, Deccan College Post Graduate and Research Institute, -411 006, India. Email:[email protected] **Archaeological Survey of India, Science Branch, Fort St. George, Chennai - 600 009, India ***Archaeological Survey of India, Science Branch, Bibi-Ka-Maqbara, Aurangabad - 431 004, India 432 Indian Journal of History of Science later caves in the form of selection of better soil facades. As result, the sun rays directly fall to the type, addition of ingredients etc in the earthen mix. caves in the afternoon. The caves of Bhaja played However, it is interesting to explore the earliest an important role as maritime trading centre earthen plaster technology prepared for application besides preaching of Buddhism in the area during on and ceilings at Bhaja caves representing the period of 100 B C to 300 A D. the first major excavation of Buddhist legend in Western India. It is reported that though Bhaja caves were excavated in 1st Century B C, earthen plastering was accomplished in 2nd century A D (Dhavalikar, 1984). Irrespective of time, Bhaja represents first major example of earthen plaster technology in India. The investigation of the composition and characteristics of Bhaja caves earthen plaster will, therefore not only throw light on the development of technology at the initial stage, but also some glimpse about understanding and knowledge of ancient Indians in the field. The Bhaja caves is situated at a distance of about 50 km to the north of famous city of Pune adjacent to Pune – Highway (Fig.1). The caves been excavated at a steep

Fig. 2. Plan of Bhaja caves The present research is inspired by the revival of traditional ancient earthen plaster technology needed for its restoration showing losses and damage to various extents during course of time. The ancient technicians all over the world mainly relied on multi layer system of plastering which considerably enhance resistance of external layer to rain water penetration besides preventing accumulation of moisture within the plaster masonry. This plastering technique also Fig.1. The location map showing the Bhaja caves. facilitated quick evaporation of moisture from within the masonry. The earthen in ancient gradient of rugged Sahayadri hills of Deccan on structures have exhibited excellent durability and coastal belt of Western India in densely forested were widely used throughout the centuries for area and during monsoon heavy rains lashes decorative coatings for ceiling and walls of both the entire coastal belt. The plan of Bhaja caves exterior and interior finish. is shown in Fig.2. The Bhaja caves are facing towards west and many of the caves did not have Mud Plaster Wall Paintings of Bhaja Caves: Composition and Performance 433

In case of mural artworks, the conservation subsequent detachment. The earthen plaster begins problems can directly be linked to the earthen to absorb moisture at 67 % relative humidity which plaster support in structural building. The causes loss of mechanical strength, degradation knowledge of traditional earthen plaster preparation of the binder and loss of painted layer due to lose is also vital in case of both restorations and repair adhesion with the background. In-situ climatic interventions of ancient cultural heritage. However, condition and application of any surface coatings technological complexity due to composition of over the paint layer will be further detrimental several layers with different micro-structures to decorative art due to differential dimensional and their role in regulating moisture movement changes, shrinkage and swelling of support layers towards external surfaces makes investiation and difference in water vapour permeability. Any about earthen plaster a little complex. The preservative coating over murals will inhibit water characteristic and nature of raw materials, their vapour transmission through various substrate selection criteria as well as relative properties of layers as paintings on earthen support is highly various components were considerat to understand water sensitive. When active deterioration is technological development of the period for observed, restoration without understanding compatible and correct intervention. Many of the causes and mechanism of deterioration may cause recipes of ancient earthen plaster are still unknown more damage in the long run (Cathers, 1999). All and often co-related to the availability of local factors of deterioration affect the original fabric resource materials and knowledge and experience and therefore proper understanding about original of artisans. From restoration point of view, earthen earthen plaster layers, clay fabric and deterioration plaster characterization is the first necessary step to process is essential. design a suitable plaster mix taking into account the Earth, a highly heterogeneous material compatibility that must exist between the original were used in the construction of shelters for and new material. For that reason, only analytical mankind for thousands of years (Mellaart, 1964). characterization of earthen plaster can provide Traditionally, the mud plaster is prepared by data for planning conservation strategies. In India, exploiting soil mainly composed of sand, silt the characterization of ancient earthen plaster in and clay with added to prevent excessive diverse geological regions of the country is still cracking during drying. For earthen support to in primitive stage (Singh, 2015; Singh, 2014). function well, an equitable distribution of sand, Conservation of decorated surfaces on earthen silt and clay is desirable. Too much silt is not a plaster support layers constitutes a specialized good binder and provides material that is prone area within the field of heritage conservation. to damage by grain breakage on account of large Published research in this field is quite limited grain size and very less contact cohesion. The due to complexity of diverse materials in different non-clays are of grain size greater than clay (< 2 support layers and availability of sufficient µm) and are divided into the grain categories of silt samples for analytical purpose (Warron,1999; (2 – 50 µm) and sand (50 µm – 2 mm) in diameter. Artioli, 2008, and Singh 2013). Research cannot Due to small surface areas, non – clays show less be accomplished at the cost of damage to the attraction for water, more irregular grain shape decorative surfaces as it is unethical to collect with reduced grain to grain contact surfaces samples for analysis from sound painted plaster. and contact cohesion much less than clays The deterioration of wall paintings on (Prost, 1998). The clays (< 2 µm) have grain earthen support is most often due to loss of cohesion shape like a sheet much thinner than wider with and adhesion of the earthen support layers and its grains attracted with electrolytic inter-particle 434 Indian Journal of History of Science forces (Basma, 1996). The clay minerals generally Bhaja caves. The stereomicroscopy, petrological consists of equal parts of expandable clays microscope, laser particle size analyzer, X-ray (illite or sepiolite) ande non expandable clays fluorescence (XRF), X-ray diffraction (XRD), (kaolinite or chlorite) with minor , calcite and scanning electron microscopy, FTIR and on-site feldspar mineral (Smith, 1989). The expandable observation under magnifying lens were selected clay minerals are sticky and responsible for as main analytical techniques. The analytical effective binding of silt and sand particles together. techniques provided variety of data about the In order to overcome inadaptability of local soil, nature and characteristics of Bhaja plaster. The other minerals such as vegetal fibre (Miller, 1934), main objective of present communication is to calcite and lime (Jerome, 1993) is added to the combine the data obtained through analytical clay to reduce shrinkage. It seems that materials techniques in an attempt to establish proper recipe like calcite, silica, ferric oxide act like a cementing for Bhaja cave plaster in addition to understand agent forming chemical bonds between the clay early technology practised by ancient Indians. micelles that may reduce shrinkage (Forth, 1990). 2. Ma t e r i a l s & Me t h o d s Proteins can react chemically with clay by One of the major drawbacks at Bhaja exchange of inorganic cations in the clay with the is obtaining sufficient quantity and numbers of organic one – a mechanism relating to the ability of decorative earthen plaster samples. Research amino acid to encourage clay flocculation (Griffin, cannot be carried at the cost of damaging our 1999). Addition of proteinaceous material in the cultural heritage and we followed the conservation earthen plaster is an ancient Indian recipe (Singh, rule that interventions should be minimum 2014) to enhance binding properties of clays. necessary. Therefore, analytical investigation It will be interesting to explore addition of any methods were limited to those that need micro proteinaceous material in the mud plaster of Bhaja samples or a few grains of the samples and also to understand composition and technology by proven to be reliable. The samples were extracted the ancient technicians. This will give additional from unpainted areas in very limited quantities. information and help to prepare compatible As cave no 12 has decorative arts on earthen materials for restoration. Besides, additions of plaster at Bhaja, samples no. 1-6 were drawn for vegetal additives in the earthen plaster works were scientific investigation from this cave. Samples the common features in the Indian sub-continent. were extracted using scalpel from the edges of the The kind of vegetal additive incorporated in the plaster showing damage and detachment from the plaster may vary according to the location of the basaltic stone carrier. This was probably the best site and its availability in the surroundings. technique for sampling that could be used in order The aim of this communication is to to limit the damage to historic plaster. characterize the earthen plaster of Bhaja caves so Visual examination under magnifying as to understand earliest clay plaster technology lens played the primary role in our understanding besides preparing a matching plaster mix for about painting technique at Bhaja that yielded restoration. Material characterisation constituted relevant information. The examination revealed primary source of our research using both two layers of earthen plaster applied on a roughly destructive and non-destructive techniques. By cut basaltic rock from which the caves were using combination of methods this work provides excavated. The most common plastering technique scientific data about chemical and mineralogical employed at Bhaja is to smooth irregular rock composition, micro-morphological characteristics, surfaces with one or more layers of mud plasters. geological and textural data of earthen plaster of Generally, two layers of mud plaster is observed Mud Plaster Wall Paintings of Bhaja Caves: Composition and Performance 435

1410, Holland X-ray fluorescence set up as per standard procedure by mounting a compressed pellet in the sample holder. For particle size analysis, the traditional hydrometer/ sieve analysis was replaced by an electronic particle size analyser (Eye Tech particle size and shape analyser, Netherland) for more precise analysis that need least quantity of samples. Only samples 1-5 which were available in higher quantity were utilised for particle size analysis. The sample particle were made to pass Fig. 3. Photograph showing two layers of mud plaster at through the path of the laser beam, causing Bhaja laser light to be scattered that resulted a unique at Bhaja (Fig. 3). diffraction pattern that solely depends on the dimension of the particles as well as wavelength There is a coarser lower layer levelling (Vitten, 1997). The sand, silt and clay percentage the roughness of the host rock whose thickness derived from particle size analysis provided major depends on the topography of the stone surfaces. findings in our study to earthen plaster. The thickness of this layer varies between 15-20 mm in the caves. There is an upper finer layer on Petrological microscopy was used to top of the inner layer that give base to the painting analyse earthen plaster samples. The thin section (layer) with thickness ranging from 10-15 mm of sample no. 2 & 3 were prepared to enable at various points. The earthen plaster layers are identification of the mineral composition. In composed of earth with characteristics very close addition, aggregates in the earthen plaster were to soil type available in the surroundings (Tamhane, identified by dissolving the plaster in distilled 1964). In a higher rain fed area of Western Ghats, water and leaving it for overnight. The aggregate there is all probability of occurrence of more of a components were subjected to petrological clayey soil for construction work. As local soil is identification to confirm their composition, likely to have been exploited for earthen plastering grain size and shape. The thin section of the by ancient Indians, there is all probability of higher earthen plaster prepared using Canada balsam clay proportions in the mud plaster of Bhaja. The was observed through Carl zeiss JENAPOL occurrence of 60-80% clay in the surrounding petrological research microscope and image taken has been reported around Bhaja (Website: mpcb. under plane polarised light at 10x magnification. gov.in/relatedtopics/CHAPTER2.pdf). However, X-ray diffraction technique was used to in an area of complex geological history, obtaining identify minerals present in the plaster. X-ray soil samples of right kind is now a problem diffraction (Philips 2404, Holland) was used especially after the growth of urban localities to determine the mineralogical composition of around ancient structures. the plaster sample no. 2 & 3 using a graphite The primary aim of our chemical analysis monochromator and CuKα radiation. The samples of earthen plaster samples was to determine its were scanned from 2θ ranging from 50 to 1200. composition by X-ray fluorescence. The major The presences of minerals were confirmed with oxides for all the six samples extracted from the the help of data file presented by JCPDS, 1994. caveno. 12 at Bhaja were identified using Phillips For FTIR spectroscopic analysis, small quantity of 436 Indian Journal of History of Science plaster sample no. 2 & 3 were taken with the help between 8.57 to 11.30 weight percentage which of sharp tip micro- scalpel and placed on freshly cannot be impurities on account of decaying basalt prepared KBr pellet. The FTIR spectra were stone. The slaked lime was probably added to obtained in the 4000-550cm-1 using Agilent 600 overcome inadaptability of local soil since it acted series FTIR spectroscopy equipped with nitrogen as cementing material with earthen mix forming cooled MCT detector. The database of FTIR chemical bonds with clay, silt and sand(Mosgnera, spectra with inorganic and organic materials were 2002;Mollinowski, 1981). The percentage of used to characterise the unknown components in alumina in the earthen mix vary between 15.69- the sample. The SEM photomicrograph of earthen 19.3 weight percentage revealing sourcing of clay plaster sample no. 2 & 3 were obtained using rich soil for Bhaja cave in resemblance to the Zeiss scanning electron microscope at a range of data observed through particle size analysis of magnification to identify the components in the earthen plaster. It appears that though the ancient plaster. Organic fibres collected after the digestion technicians of Bhaja sourced clay rich soil for of the plaster samples were also observed under compactness of the plaster, yet they deliberately Olympus magnus MS2 and LABOMED CSM2 mixed slaked lime for its better strength and stereomicroscope to identify the fibres used as durability. The clay proportion between 60-80% organic additives of binder in the . has already been reported in the surrounding soil near Bhaja caves (Singh, 2015). This indicates sourcing of local soil for earthen plaster works 3. Re s u l t s a n d Di s c u s s i o n whose properties were further modified by 3.1 Chemical composition of earthen plaster addition of other ingredients. The remarkable red colour of the earthen plaster is due to the presence Eighteen caves excavated from Deccan of iron oxide, detected between 12.29-15.11% basalt are present at Bhaja. However, only one in the plaster. As Bhaja caves represents the (cave no. 12) has either layers of earthen plaster earliest example of earthen plaster technology, the or earthen plaster with painted surfaces. The chemical analysis data reflect historical / technical chemical composition of earthen plaster in the development of the period and sourcing of better form of major oxides determined using X-ray soil type and improvement of technology in later fluorescence is shown in Table 1. plaster works in India [Singh, 2015; Singh, 2014, From the data it is observed that slaked and Singh 2015). slightly dolomitic lime has invariably been mixed in all the earthen plaster to enhance 3.2 Petrological Analysis binding properties of the local soil. The combined The earthen plasters of Bhaja caves were percentage of calcium and magnesium calcites vary observed under polarised microscope and the

Table 1: Chemical Composition (% byweight) of earthenplaster of Bhaja caves.

Sample Na2O MgO Al2O3 SiO2 P2O5 K2O CaO TiO2 MnO Fe2O3 LOI % % % % % % % % % % ASI11M 0.83 2.47 19.3 44.15 0.3 0.56 6.1 2.67 0.14 14.85 8.63 ASI12M 1.29 3.63 15.69 45.2 0.3 0.76 7.96 1.95 0.14 12.29 10.79 ASI13M 0.9 2.52 18.71 43.28 0.24 0.52 6.16 2.69 0.16 14.77 10.05 ASI14M 1.2 2.35 18.38 44.83 0.25 0.61 6.56 2.56 0.15 15.11 8 ASI15M 0.9 3.5 16.58 44.35 0.3 0.88 7.8 1.85 0.16 13.52 10.16 ASI16M 1.1 2.42 17.58 45.2 0.29 0.79 7.3 2.5 0.15 13.49 9.18 Mud Plaster Wall Paintings of Bhaja Caves: Composition and Performance 437 principal minerals observed were plagioclase, kaolinite, mica, quartz, iron oxide etc. along with vegetal remains mostly rice husk in all the samples. The creamy white colour lime is found mixed in fine grains of sub – angular to sub – rounded transparent to honey red colour quartz grains. The thin section of sample no. 2 & 3 were examined under plane polarised light and the result is shown in Fig.4 taken at 10 x magnifications. In Fig.4 light to dark coloured medium to fine textured fabric is seen.

Fig. 5. Thin section images of Bhaja caves.

3.3 Aggregate Analysis The earthen plaster of Bhaja (sample no. 2 & 3) was dissolved in 10% hydrochloric acid for overnight followed by subsequent washing of the aggregates till neutral pH. The aggregates were sieved after drying and separated as per grain size. Fig. 6 shows the grain size of the aggregates mixed in the plaster. It is observed that coarse to fine sand aggregates of basaltic origin were mixed in the earthen plaster for strength and durability. The proportion of fine sand was observed in higher Fig. 4. Thin section Images of Bhaja caves. quantity to that of coarse sand.

The image showed irregular grains of quartz and silicate embedded in kaolinite and chlorite clay ground mass. The shiny calcite grains intermixed with silica ground mass along Fig. 6. Aggregates in mud plaster of Bhaja caves. with muscovite embedded in kaolinite clay are seen. In the thin section in Fig. 5, abundance of From the grain shape of the aggregates, kaolinite mass with embedded iron oxide minerals Fig. 6, it is observed that majority of grains are sub are clearly observed. The presence of iron oxide in angular to sub rounded which together constitute the samples is due to preparatory material made up more than 80 % of the aggregate grains. The rice of crystalline and amorphous phase rich in ferrous husk as vegetal additives was prominently noticed substances. The petrological data of the earthen in the plaster at Bhaja. The shrinkage of the soil plaster are in agreement to XRD analysis of the was significantly tailored with the influence plaster used for determination of mineralogical by addition of calcite, aggregates and vegetal composition. additives in the plaster works. 438 Indian Journal of History of Science

3.4 Particle size Analysis clay proportion consisting of both expandable The particle size analysis of earthen plaster and non expandable clay envisaged through of Bhaja provided distribution curve through thin section / SEM analysis may cause moisture which the soil was characterised. The type of the movement within the earthen plaster. The Bhaja earthen support was assessed through the presence caves are situated in Western Ghats, a very high of sand, silt and clay in the plaster. As obtaining rain fall area during monsoon period. The humidity higher quantity of sample is not possible for the inside the caves reaches around 90% during rainy decorative arts of Bhaja, we relied on laser particle season. During this period the expandable clay size analyser which needs smaller samples and the like sepiolite, chlorite etc. present in the plaster results are more precise, reliable and faster. The starts absorbing moisture whenever humidity earthen plaster samples no. 1-5 was examined reaches above 67%. On absorption of moisture under laser diffraction analysis. Three trials for the clay part shows swelling behaviour resulting each measurement were taken and the average initiation of disintegrationof the earthen plaster. reported in the data. The particle size analysis In the summer season, the humidity inside the curve of Bhaja plaster is shown in Fig.7. caves drops down to around 40% causing loss of absorbed water. The regular absorption and loss From the particle size analysis, it is of moisture from the clay part of the plaster cause observed that the earthen plaster of Bhaja is much disintegration of the plaster in the long run. finer and contains far less silt size particles. The grain size analysis showed the majority of grains The earthen plaster of Bhaja based on their sand, silt and clay proportions were plotted on sand-silt-clay ternary diagram (Fig. 8).

Fig. 7. The particle size analysis curve of Bhaja plaster. are of clay sized (more than 65%), followed by sand sized (20-28%) and least the silt sized (7-15%). Due to presence of more proportion of clay size particle, the earthen plaster of Bhaja Fig. 8. Sand-silt-clay ternary diagram of Bhaja plaster. shows compactness. The compactness of the earthen plaster was further improved by addition From the ternary diagram, it is observed of slaked lime, iron oxide etc. into the plaster. that clay soil (clay proportion above 65%) was However, the particle size distribution of soil sourced for the preparation of earthen plaster. The structure precisely influences humidity transfer higher clay proportion caused extensive damage within the plaster (Katheen, 1997). The higher to the earthen plaster of Bhaja due to its swelling/ Mud Plaster Wall Paintings of Bhaja Caves: Composition and Performance 439 contraction behaviour. It is to be mentioned that in magnesium carbonate to calcium carbonate. The the later caves silt-loam type of soil was selected IR spectrum also showed a small peak of amides for earthen plaster displaying much higher stability around 1650 cm-1 pointing addition of some and strength. The ancient earthen plaster in India adhesive juice in the plaster works of Bhaja caves. are also said to be invariably mixed with organic This N-H band is due to presence of primary and adhesive (Svaramamurti, 1978) for enhanced secondary amides from proteinaceous and fatty binding. The protein of the adhesive juices acted materials mixed for adhesive purpose. The IR with clay particles causing clay flocculation. spectra showed characteristic band at around 3500 However, with time owing to high absorption of cm-1 due to free hydroxyl ions of the water. moisture by clay particle, the adhesive materials also showed tendency to dissolve and loose its 3.6 XRD Analysis properties. This is what happened to the earthen In the present study, the x-ray diffraction plaster works at Bhaja which in turn caused of sample no. 1 & 4 of Bhaja were carried out and disintegration and loss of decorative arts at the mineralogical data obtained from XRD are numerous places inside the caves. The particle size shown in Fig.10. analysis supports the data obtained through thin The major identified minerals in Bhaja section/ SEM photomicrograph of the plaster. plaster observed through XRD study are 3.5 FTIR Analysis quartz [SiO2] (dinÅ=3.345, 4.265)and sepiolite [Mg4Si6O15 (OH) 2·6H2O] (d in Å=3.345, 4.265, A few fragments of earthen plaster of 2.85). Calcite [CaCO3] (d in Å=1.981, 1.818) sample no. 1-3, Bhaja caves were observed under observed in XRD patterns for finer particle size Fourier Transform Infrared (FTIR) spectroscopy fraction may come from carbonated lime. Peaks with identical peaks. The FTIR spectrum of sample of Kaolinite [Al4 (Si4O10) (OH) 8] (d in Å=1.672, no. 2 is only shown in Fig. 9 as an example. 1.542) and orthoclase [KAlSi3O8] (d in Å=3.25, The most characteristic band of silicate 3.19) which is the siliceous clay mineral are also visible in XRD pattern, its occurrence is as SiO2 tetrahedra is seen at a spectral region at around 1000 cm-1. A very small calcium carbonate supported by the SEM and petrological analysis. stretching peak at 1423 cm-1 is observed in FTIR Identification of the above mentioned constituents spectrum of earthen plaster. A very small peak confirms the presence of clay base and siliceous at 748 cm-1 denotes presence of magnesium filler for Bhaja plaster.As the mineralogical carbonate which is a unique spectra differentiating composition depends on the regional geology

Fig. 9. FTIR Spectrum of Mud plaster sample No. 2. 440 Indian Journal of History of Science

The SEM photomicrograph (Figs. 12 a, b and c) of the sample no. 3 taken at magnification of 2000, 1000x and 3000x are shown in Figs. 12 a & c pointing clay mineral structure of Kaolinite. The individual Kaolinite arranged face to face into an elongated stack, called a ‘verm’. In this, a secondary growth of blocky kaolinite crystals can be observed in a crack within the verm. Along Fig. 10. XRD Spectrum of Mud plaster sample, Bhaja caves. with Kaolinite, elongated detrital biotic mica grain compacted between quartz grains within and climatic conditions, it denotes occurrence of clay matrix is seen. An open interconnected pore clayey soil in the surrounding of Bhaja caves in lined with ribbons forming a mat like structure which local sand was mixed as aggregate. coating the detrital grain surfaces and also bridging the pores between grains is observed in 3.8 SEM Analysis the SEM image. Due to this permeability barrier The scanning electron microscope is created for moisture flow. This type of clay photomicrograph of the earthen plaster of Bhaja structure severely reduces permeability without cave for sample no. 2 and 3 are shown in Figs. affecting porosity. The higher magnification 11and 12(a-d). In the photomicrograph of sample photomicrograph of the bridge revealed that no. 2 taken at magnification of 1000x, patches of the earthen plaster is composed of inter wired calcites are seen between detrital quartz grains clay ribbons of filamentous illite-sepiolite clay and calcite appears slightly dissolved in quartz minerals. In Fig.12 b at magnification 1000x grain. Quartz grain is porous, well rounded with the microstructure of albite feldspar along with minor authigenic quartz overgrowths and pore filamentous illite can be observed. lining clays are present in SEM image. From In photomicrograph of sample no 3 in Fig.11 the presence of iron oxide particle cluster Fig.12 d taken at the magnification of 3000x, and the remains of vegetal root is also observed. presence of an authigenic chlorite platelets (arrow) The figure also shows thin coating of filamentous stacked face to face is observed. The smaller illite on the surface of detrital grain. stacks of circular chlorite are indicated by arrows.

Fig.11. SEM images of Mud plaster, Bhaja caves showing quartz, calcite, remains of vegetal root and iron oxide. Mud Plaster Wall Paintings of Bhaja Caves: Composition and Performance 441

Fig. 12 (a-d) SEM images of Mud plaster, Bhaja caves showing Kaolinite, Sepiolite, Illite, Mica, Feldspar and Calcite.

The chlorite is formed in a depression within origin. The major minerals noticed are plagioclase, an altered rock fragment. This interpretation kaolinite/ sepiolite, clay, mica, quartz, iron oxide is consistent with petrological, XRD and other etc. reflecting byproduct of disintegrating basaltic analysis techniques of the earthen plaster. rock. The presence of N-H band in FTIR spectra reflects addition of proteinaceous adhesive in the 4. Co n c l u s i o n plaster. The plaster is mainly composed of thin From the analytical examination, it filamentous illite embedding quartz and silicate is observed that the earthen plaster of Bhaja minerals. The result is important for preparation contains many fine particles due to presence of of compatible mud plaster for restoration of Bhaja >65% clay that gave flexibility, strength and caves. cementing properties to the plaster. To overcome inadaptability of raw soil slaked lime and rice husk Ac k n o w l e d g e m e n t s were deliberately mixed to give strength and stop The authors are grateful to Prof. D.N. cracking during drying for the plaster. The majority Singh, Dr. Kannan Iyer and Dr. Naveen Kosi of the aggregates (H≈80%) mixed in the plaster of Indian Institute of Technology, Mumbai for are sub rounded to sub angular shape of basaltic their help in the investigation. The help extended 442 Indian Journal of History of Science by Dr. T.R. Raveendran, IGCAR, Kalpakkam Mosgnera, M.J, Benitez, D., Perry, S.H. Pore structure in & Shri. Deepak Gupta, ASI is gratefully mortars applied on restoration. J. Cem. Conc. Res. 32(2002): 1883-8. acknowledged. We are especially thankful to Prof. Vasant Shinde, Dr. P.D. Sabale, Deccan Mollinowski, R. Ancient mortars and concrete durability aspects, mortars, and grouts used in Post Graduate & Research Centre, Pune for their conservation of historic building, Proceeding of the support. We are thankful to our Director General symposium, ICCROM, Rome 1981, pp.341-350. and Director (Science) at Archaeological Survey Prost, R., Konntic, T., Benchare, A., Haurd, E. State of India, New Delhi for their constant support and location of water absorbed in clay minerals- during the course of this research. Cosequence to the hydration and swelling-shrinkage phenomenon. J. Clay and Clay minerals, 14.2 (1998):117-31. Bib l i o g r a p h y Singh, M., Arbad, B.R. Characterization of 4-5th century Artioli, D., Capanna, F., Giovagnoli, A., Marcone, A., A.D. earthen plaster support layers of Ajanta mural Rissoto, L. and Singh, M.The mural painting of paintings. J. Construction and Building Materials, 82 , part II: Non-destructive Investigation (2015): 142-154. and micro-analysis of execution technique and state of conservation in Art, 9th International Conference Singh, M., Arbad B.R. Characterization of traditional mud Jerusalem. Israel. 2008. mortar of the decorated wall surface of . J. Construction and Building Materials, 65(2014): Basma, A. A., Al Homound Azm S., Husein Malkawi 384-395. Abdallah I, Al Bashabsheh Mohamed A. Swelling shrinkage behavior of natural expansive clays. J. Appl. Singh, M. and Arbad, B.R. Carrying capacity of cave murals Clay Sci.,11.2-4(1996):211-27 of Ajanta. IJSER 4 (2013) Cathers. Assessing causes and mechanism of detrimental Singh, M. and Arbad, B.R. Ancient Indian painting recipe charges to the wall paintings In: Cowing R. Heritage and mural art technique at Ajanta. Int. Jour. of Cons. A,(ed.) Conserving the Painted Plaster, Post prints Sci , 5.1(2014): 35-50. of a conference organized by the English Heritage, London 1999, pp.67-74. Singh, M., Vinodh Kumar, S., Waghmare, S. Characterization of 6-11th century A.D. decorative plasters of rock Dhavalikar, M. K. Late caves of western India, cut caves of Ellora, J. Construction and Building Deccan College Post Graduate and Research Institute, Materials, 98(2015): 156-170. Pune, 1984. Sivaramamurti, C. Citrastra of the Viudharmottara, Forth, H.D. Fundamental soil science, 8thed, Viley, Newyork, 1990. Kunal Publication, New Delhi, 1978. Griffin, T.J. Earth grounds in wall painting conservation, Smith, E.W., Austin, G.S. pressed earth and rammed An investigation of their working properties and earth industries in new Mexico, Bur. Mines.Miner. Res. performance characteristics, MA thesis, Courtland Bull. 127(1989) Institute of Arts.1999. Sundarajan, K.V. Beginning of the temple plan, Prince Jerome, P. Analysis of bronze age mud bricks from —Bulletin No. 6(1957-59):74-81. th palaikastro, crete, 7 International conference at the Tamhane, R.V., Motiramani, D. P., Bali, Y. P., Roy, L. D. study and construction of earthen architecture, Silves, Soils: Their chemistry and fertility in Tropical Asia, Portugal, 24-29 Oct, 1993381-386. 1964 Katheen F. Clift dwelling walls- the earthen plaster project Vitten, T.S. Sadler, Y.L. Particle size analysis of soils using at Mesa Verde, CRM bull., 20.10 (1997):38-9. laser light scattering and x-ray absorption technology, Mellaart, J.A Neolithic city in Turkey, J. Sci Am, 210(1964): J. Geotech Test. 20(1997): 63-73. 94-104. Warran, J. Conservation of Earth Structures, Butterworth, Miller, T. Adobe and sun dried brick for farm Building, Heinemann, Oxford1999 Farmers’s Bulletin No. 1720, US Dept. of Agriculture, Washington DC,1934 Website: mpcb.gov.in/relatedtopics/CHAPTER2.pdf.